Traditional toilet assembly design utilized bolt fasteners to connect the tank to the bowl with a polymer washer on the inside of the tank through two pieces of vitreous china followed by a steel washer and a fastener nut on the outside of the bowl. This assembly was intended not only to mechanically secure the tank to the bowl, but also prevent the water or water/chemical fluids from leaking out of the tank. Once the bolts, steel and polymer washers and nuts were assembled in the proper order, each fastener assembly was tightened using wrenches and/or screwdrivers. In addition to the labor intensive nature of this process, components of the fastener assembly were lost and assemblies were improperly secured. In addition, washer components often only provided a marginal compression seal often resulting in leaks from the tank. Due to the design of this fastening system, the metallic bolt is continuously submerged in water on the inside of the tank and exposed to condensate water on the outside of the tank. These conditions cause corrosion of the bolt, which, in turn, can result in leaks and/or difficulty in removing the bolts when servicing the toilet.
Fasteners, such as bolts of mild or stainless steel, brass or other metals, that are to be exposed to moisture and chemicals used in the plumbing industry are typically made from bars or rods that may have been bare or plated or galvanized, usually with zinc. The plating process is typically either by electrolytic deposition of zinc or via dipping the bolt fastener into a molten zinc bath or pot. The latter is characterized as a “hot dipping” process.
The metal used for these bolt fasteners may be composed of various alloys that demonstrate significant property differences depending upon the degree of cold working, differences in the basic metal constituents, and whether or not a stress relieving (patenting or annealing) process stage has been introduced.
Such bare and plated bolt fasteners are commonly used in the plumbing industry. In the case of a toilet, several (typically two or three) bolt fasteners were used to mechanically connect the water holding vessel, commonly referred to as the “tank”, to the toilet bowl. This was accomplished by inserting the bolt through matching holes in the tank and bowl with a nut on the bowl side providing the balance of the mechanical assembly between the tank and bowl. Since the bolt head and portion of the bolt shank immediately adjacent to the head are installed on the inside of the tank, they are continuously exposed to water and chemical additives. Corrosion is an electrochemical process that allows a refined metal to revert to its native oxide state (rust). In order for corrosion to occur, an electrolyte must be present. The water or water/chemical mixture in the tank acts as this electrolyte and reacts with the exposed bolt surfaces causing them to corrode. When the bolt corroded, the fastener system was difficult or impossible to remove and replace using common hand tools.
The portion of the bolt fastener shank that extends from the outside of the bowl and onto which the bolt has been assembled does not come into contact with the water or water/chemical electrolyte on the inside of the tank. However, condensate water often forms on the exterior of the tank, especially in humid environments. This condensate water often travels down the bowl and onto the bolt fastener shank on the underside of the bowl. Since condensate water also acts as an electrolyte, corrosion often occurred on the bolt shank making it difficult or impossible to remove and replace the tank to bowl fastener using common hand tools.
In order to improve the corrosion resistance of the bolt fasteners, improve the seal against tank leaks, improve ease of installation and reduce fastener assembly part count, there is a need or desire for a fastener system that reduces corrosion and more effectively prevents the tank from leaking. There is also a need for a bolt fastener system that is easier to install using the minimum number of commonly available hand tools.